This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-359462, filed Dec. 17, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a card-type electronic apparatus such as a portable-type multi-media card having a built-in flash memory, and also to a method of manufacturing such a card-type electronic apparatus.
In recent years, portable-type multi-media cards having a build-in flash memory have come to be widely used. The multi-media cards of this type, which have a small-size and are easily used with high quality, are expected to be applied to portable-type information apparatuses such as portable telephones and multi-media apparatuses such as music players and digital cameras, as external storage media for storing video images requiring a large capacity, voice and other data.
The conventional multi-media card is constituted by a card case made of a synthetic resin and a memory module. The card case is standardized to have length and width dimensions corresponding to a small post-stamp size, and also to have a thickness of approximately 2 mm. This card case is constituted by a first case having a bottom wall and a second case having a top wall. The first case and the second case are joined to each other by aligning the outer circumferential edge of the bottom wall and the outer circumferential edge of the top wall face to face and fitting them to each other.
The memory module is housed inside the card case. The memory module has a circuit substrate and a plurality of electronic parts mounted on this circuit substrate. The circuit substrate is placed inside the card case in parallel with the bottom wall of the first case and the top wall of the second case. A plurality of power-apply terminals having a rectangular shape are placed on the front end of the circuit substrate. The power-apply terminals are aligned in a row in the width direction of the card case, and exposed to the outside of the card case through an opening formed in the bottom wall.
The electronic parts include a semiconductor package constituting a large capacity flash memory, an LSI chip and capacitors constituting a controller, etc., and these electronic parts are electrically connected to the power-apply terminals. For this reason, in the conventional multi-media card, the circuit substrate and the electronic parts are housed inside the card case in a stacked manner in the thickness direction of the card case.
The circuit substrate of the memory module has a first surface opposing the bottom wall of the first case and a second surface opposing the top wall of the second case. Here, in the conventional memory module, there are two cases in which the electronic parts are mounted on both of the first and second surfaces in a separate manner and in which all the electronic parts are mounted on either the first surface or the second surface of the circuit substrate as one lot.
In the case of the memory module with a circuit substrate having the electronic parts mounted on the first and second surfaces thereof, it is necessary to maintain inside the card case a space having a height dimension set by adding at least the thickness of the circuit substrate, the height of the electronic parts on the first surface and the height of the electronic parts on the second surface. Consequently, the thickness dimension of the card case is increased, causing a problem with the thinness of multi-media cards.
In the case of the memory module with a circuit substrate having the electronic parts mounted on only one side thereof, the circuit substrate can be placed along the bottom wall or the top wall of the card case. For this reason, it is possible to make the card case thinner.
In this structure, however, most of one surface of the circuit substrate is occupied by the mounting space of the electronic parts. Consequently, the power-apply terminals need to be placed on the surface of the circuit substrate opposite to the electronic parts. Here, since the power-apply terminals need to be exposed to the outside of the card case through the opening in the bottom wall, the circuit substrate needs to be placed along the bottom wall. This causes an extreme reduction in the dimension from the opening end of the opening to the power-apply terminals.
In other words, since the thickness of a multi-media card is as thin as approximately 2 mm, the thickness of the bottom wall of the card case needs to be as thin as approximately 0.3 mm. For this reason, it is not possible to provide a sufficient step between the outer surface of the bottom wall and the power-apply terminals. Consequently, for example, when a multi-media card is pinched by the hand, the finger tip tends to touch the power-apply terminals, with the result that the electronic parts might be seriously damaged by static electricity possessed by the human body. Moreover, a finger print or oil components from the finger tip might adhere to the power-apply terminals, resulting in disconnection.
Furthermore, in the conventional multi-media card, the card case is assembled by applying vibrational energy derived from ultrasonic waves to the butt portions of the first case and the second case and joining the two cases to each other. More specifically, the outer circumferential edge of the first case and the outer circumferential edge of the second case are aligned to butt against each other, and the outer circumferential edges of these cases are then pinched by a ultrasonic wave head and a fixed table; thus, in this state, the ultrasonic wave vibration is applied to the outer circumferential edges of the first and second cases. Consequently, the outer circumferential edges of the first and second cases are thermally melted and joined to each other all around the edges to form a card case.
In the conventional card case, the thickness dimension of the outer circumferential edges of the first and second cases is set to be constant all around the edges. For this reason, when the outer circumferential edge of the first case and the outer circumferential edge of the second case are aligned to butt against each other, the thickness of these butt portions becomes greater, thereby making the gap between the ultrasonic wave head and the fixed table greater. As a result, when the butt portions of the outer circumferential edge of the first case and the outer circumferential edge of the second case are subjected to ultrasonic wave vibration and allowed to melt, the capacity of the butt portions that are thermally affected becomes too great. Therefore, upon completion of the melt-joining of the first case and the second case, a thermal strain tends to occur in the outer circumferential portion of the card case, and the residual stress due to the thermal strain becomes greater.
Consequently, the card case might be deformed in a warping manner after the melt-joining process, and the flatness of the bottom wall and the top wall of the card case might be impaired. In addition, the above-mentioned residual stress tends to cause the outer circumferential portion of the card case to deform outwards in a swelling manner, resulting in degradation in the dimensional precision in the card case.
Moreover, in the conventional multi-media cards, the circuit substrate of a memory module is firmly fitted to the inside of the first case. Here, the outer circumferential edge of the first case is thicker and has a greater capacity in receiving the ultrasonic vibration; therefore, the ultrasonic vibration applied to the outer circumferential edge is not readily absorbed by the fixed table. For this reason, the ultrasonic vibration, applied to the outer circumferential edge of the first case, as it is, is allowed to reach the electronic parts through the circuit substrate, with the result that the precise electronic parts might be seriously damages by the ultrasonic vibration, or might be broken.
It is a first object of the present invention to provide a card-type electronic apparatus which, in spite of its structure having electronic parts mounted on both of first and second surfaces of its circuit substrate, can provide a thin, compact card case.
It is a second object of the present invention to provide a card-type electronic apparatus in which the power-apply terminals can be placed in a recessed position inside an opening, thereby making it possible to prevent the power-apply terminals from being touched by the hand.
It is a third object of the present invention to provide a card-type electronic apparatus which can prevent deformation in the card case caused by ultrasonic wave melt-joining, thereby making it possible to improve the dimensional precision in the card case, and which also makes the ultrasonic vibration applied at the time of the melt-joining of the card case less likely to be transmitted to the electronic parts, thereby making it possible to prevent the electronic parts from being damaged.
In order to achieve the first object, the card-type electronic apparatus of the present invention is provided with a flat card case and a circuit module housed in the card case. The circuit module is provided with a circuit substrate having a first surface and a second surface positioned on the side opposite to the first surface, at least one first electronic part mounted on the first surface of the circuit substrate and at least one second electronic part mounted on the second surface of the circuit substrate. Here, the first electronic part having the greatest height dimension on the first surface and the second electronic part having the greatest height dimension on the second surface are placed in an offset manner from each other without facing each other with the circuit substrate interpolated in between. Moreover, the circuit substrate is provided with a step portion for allowing the first electronic part having the greatest height dimension on the first surface and the second electronic part having the greatest height dimension on the second surface to be shifted in an approaching direction with each other along the thickness direction of the card case.
With this arrangement, the first electronic part having the greatest height dimension on the first surface and the second electronic part having the greatest height dimension on the second surface are shifted in a manner so as to approach each other along the thickness direction of the circuit substrate. Thus, a space to be maintained inside the card case so as to house the memory module is set to a smaller height dimension obtained by subtracting the gap of the step portion of the circuit substrate from a value obtained by adding the heights of the first and second electronic parts having the greatest heights to the thickness of the circuit substrate. Consequently, as compared with the conventional apparatus having a flat circuit substrate, the card case can be made thinner by a dimension corresponding to the gap of the step portion. Therefore, although it has a construction with a circuit substrate having electronic parts mounted on both of the first and second surfaces, this construction still makes it possible to provide a thinner, compact card case.
Moreover, in order to achieve the first object, the card-type electronic apparatus of the present invention is provided with a flat card case and a circuit module housed in the card case. The circuit module is provided with a circuit substrate having a first surface and a second surface positioned on the side opposite to the first surface, at least one first electronic part mounted on the first surface of the circuit substrate and at least one second electronic part mounted on the second surface of the circuit substrate. Here, the first electronic part having the greatest height dimension on the first surface and the second electronic part having the greatest height dimension on the second surface are placed in an offset manner from each other without facing each other with the circuit substrate interpolated in between. Moreover, the circuit substrate is inclined along the thickness direction of the card case so that this inclined structure allows the first electronic part having the greatest height dimension on the first surface and the second electronic part having the greatest height dimension on the second surface to be shifted in an approaching direction with each other along the thickness direction of the card case.
With this arrangement, it is possible to reduce the height dimension of a space to be maintained inside the card case so as to house the memory module. Therefore, although it has a construction with a circuit substrate having electronic parts mounted on both of the first and second surfaces, this construction still makes it possible to provide a thinner, compact card case.
Moreover, in order to achieve the second object, the card-type electronic apparatus of the present invention is provided with a flat card case having an opening and a circuit module housed in the card case. The circuit module is provided with a circuit substrate having a first surface on which a power-apply terminal that is exposed to the opening is placed, and a second surface positioned on the side opposite to the first surface, and an electronic part that is mounted at least on the second surface of the circuit substrate and that is electrically connected to the power-apply terminal. The circuit substrate is provided with a first mount area in which the power-apply terminal is positioned and a second mount area in which the electronic part is placed. The first mount area and the second mount area are offset from each other without overlapping with each other on the circuit substrate, and are shifted from each other along the thickness direction of the card case.
With this arrangement, the shifting direction of the first mount area is regulated so that the power-apply terminal can be shifted in a departing direction from the opening of the card case. For this reason, the power-apply terminal can be placed at a recessed position inside the opening, thereby preventing the power-apply terminal from being touched by the finger tip when the card case is pinched by the fingers. Therefore, it becomes possible to prevent the electronic part from being damaged by static electricity possessed by the human body, and also to prevent the power-apply terminal from finger prints and oil components from the finger tip.
In order to achieve the third object, the card-type electronic apparatus of the present invention is provided with a card case made of a synthetic resin, housing an electronic part. This card case includes a first case having an outer circumferential edge and a second case having an outer circumferential edge, and the outer circumferential edge of the first case and the outer circumferential edge of the second case are aligned to butt against each other, and integrally melt-joined to each other by applying ultrasonic wave vibration to these outer circumferential edges. Moreover, the card case is provided with a cut section that is cut out so as to reduce the thickness thereof and that is formed at a position corresponding to at least one portion of the outer circumferential edges; thus, the first and second cases are melt-joined to each other at least at the position corresponding to the cut section.
In order to achieve the third object, the card-type electronic apparatus of the present invention is provided with a card case made of a synthetic resin, which comprises a first case and a second case that is aligned to butt against the first case, at least either the outer circumferential edge of the first case or the outer circumferential edge of the second case being provided with a cut section that is cut out so as to reduce the thickness thereof, and an electronic part housed inside the card case.
The method of manufacturing this card-type electronic apparatus in accordance with the present invention is provided with a first step of allowing the electronic part to be interpolated between the first case and the second case, and a second step of aligning the outer circumferential edge of the first case and the outer circumferential edge of the second case so as to butt against each other, sandwiching the butt outer circumferential edges with a ultrasonic wave head and a table at least at the position corresponding to the cut section, and melt-joining the first case and the second case by applying ultrasonic vibration to the outer circumferential edge of the first case and the outer circumferential edge of the second case through the ultrasonic wave head.
With this card-type electronic apparatus, the outer circumferential edge of the first case and the outer circumferential edge of the second case are melt-joined to each other by applying ultrasonic wave vibration at the position corresponding to the cut section. At the position of the cut section, the thickness of the butt portions of the first case and the second case is reduced; therefore, when the butt portions of the two cases are subjected to ultrasonic wave vibration and allowed to melt, the butt portions have a capacity reduced by the cut section in receiving the ultrasonic vibration. Thus, it is possible to reduce the thermal strain occurring in the first and second cases, and consequently to reduce a residual stress due to the thermal strain.
As a result, it is possible to avoid cases in which, after the first and the second cases have been melt-joined, the card case is deformed in a warping manner, and the outer circumferential edges of the first and second cases are deformed outwards in a swelling manner; thus, it becomes possible to well-maintain the degree of flatness and dimensional precision of the card case.
Moreover, the existence of the cut section makes it possible to reduce the thickness of the butt portions of the first case and the second case so that the gap between the ultrasonic wave head and the table is narrowed. For this reason, the ultrasonic wave vibration applied to the butt portions of the first case and the second case is readily absorbed by the table. Therefore, the ultrasonic wave vibration is less likely to be transmitted to the electronic part inside the card case, thereby making it possible to prevent the electronic part from being damaged by the ultrasonic wave vibration beforehand.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.